Liquid, such as high-purity semiconductor chemicals, general chemicals, and so forth, is generally filled in a liquid tank, such as a polyethylene tank or the like, in a production factory, and is shipped in a state in which a lid is attached to a vent plug portion formed in the liquid tank for filling/drawing out liquid. A siphon tube system is a known method of drawing out liquid contained in such a liquid tank, in which the liquid is supplied outside a container by gas pressure generated by introducing gas, such as air or the like, into the container.
With this system, a plug provided with a siphon tube, which serves as a liquid flow channel, and a gas supplying channel is attached to the vent plug portion after removing the lid attached to the vent plug portion of the liquid tank. Then, a liquid flow channel for drawing out the liquid and a gas flow channel for introducing gas are formed by connecting the plug to a socket to which a tube for drawing out the liquid outside the liquid tank and a tube for introducing gas can be individually connected.
Because such a liquid-tank connector is threaded to a container (vent plug portion), the connector needs to be rotated when attaching it to the container. Because of this, with a structure in which a tip of a siphon tube is curved so as to reduce the amount of liquid remaining in a container, it is difficult to place an opening provided at the tip thereof in the deepest region due to the rotation of the connector, and, as a measure for coping with this, a connector having a structure that connects a joining portion and a main unit in a manner allowing them to be relatively rotated about a center axis has been proposed (for example, see Japanese Unexamined Patent Application, Publication No. 2006-182400).